What is topographic wetness index?

Topographic Wetness Index is used to quantify topographic controls on hydrological processes. Topographic Wetness Index (TWI) can also be used to characterize biological processes including forest site quality, vegetation patterns, and annual net primary production (Beven & Kirkby, 1979; Sorenson, et al., 2006).

What is Saga wetness index?

The ‘SAGA Wetness Index’ is, as the name says, similar to the ‘Topographic Wetness Index’ (TWI), but it is based on a modified catchment area calculation (‘Modified Catchment Area’), which does not think of the flow as very thin film.

Is there a scale for wetness?

The TWI has been used to study spatial scale effects on hydrological processes. The topographic wetness index (TWI) was developed by Beven and Kirkby within the runoff model TOPMODEL. The topographic wetness index is unitless.

What two terms define the topographic wetness index?

The topographic wetness index (TWI) was developed by Beven and Kirkby (1979) within the runoff model TOP- MODEL. It is defined as ln(a/tanβ) where a is the local upslope area draining through a certain point per unit con- tour length and tanβ is the local slope.

What factors lead to a wet area when using the topographic wetness index?

Topographic wetness index (TWI) describes how likely an area is to be wet based on its specific catchment area and local slope as described in Eq. (2), where As is the specific catchment area and slope is the slope of the grid cells in degrees (Beven and Kirkby 1979).

What is sediment transport index?

The sediment transport index characterises the process of erosion and deposition. Unlike the length-slope factor in the Universal Soil Loss Equation (USLE) it is applicable to three-dimensional surfaces (Burrough et al. As is the upstream area and β is the slope at a given cell.

What is TWI in GIS?

Topographic Wetness Index (TWI) that quantifies topographic controls of basic hydrological. processes (Schillaci et al., 2015). TWI is derived through interactions of fine-scale landform. coupled to the up-gradient contributing land surface area according to the following relationship. (Beven et al., 1979):

What is specific catchment area?

[1] Specific catchment area, defined as the area of land upslope of a width of contour, divided by the contour width, is a commonly used quantity in hydrology to describe complex terrain for analyzing water flow on hill slopes; it can be a surrogate for water discharge per unit flow width.

What is terrain ruggedness index?

The topographic ruggedness index (TRI) was developed by Riley, et al. ( 1999) to express the amount of elevation difference between adjacent cells of a DEM. It calculates the difference in elevation values from a center cell and the eight cells immediately surrounding it.

What is Stream Power Index?

The Stream Power Index (SPI) is a measure of the erosive power of flowing water. SPI is calculated based upon slope and contributing area. SPI approximates locations where gullies might be more likely to form on the land- scape.

How is catchment area discharge calculated?

Q = 0.028 PfIcA = 0.028 x 0.10 x 0.60 x 2.98 x 80,000 = 400 cum/sec. When the catchment area is of clayey soil lightly covered, P from table 3.3 = 0.50, values of A, f and Ic remaining as before. Q = 0.028 PfIcA = 0.028 x 0.50 x 0.60 x 2.98 x 80,000 = 2003 cum/sec.

How do you calculate catchment area for a drain?

It is simple. Just use your geometrical skills to calculate rooftop area or any other catchment area of small size. Using some simple multiplication and additions you can come up with the catchment area value in square meter. Measure length and width of the roof in meters and multiply both to get area in square meters.

Which is the best description of the wetness index?

Topographic wetness index. The topographic wetness index (TWI), also known as the compound topographic index (CTI), is a steady state wetness index. It is commonly used to quantify topographic control on hydrological processes.

When was the topographic wetness index ( TWI ) created?

The topographic wetness index (TWI) was developed by Beven and Kirkby within the runoff model TOPMODEL. The topographic wetness index is unitless.

How to calculate the soil wetness index ( SM )?

SM on EFAS-IS is the mean SM for the two upper layers. The below formulas calculate SM for each point. You will need to derive the soil depth for each layer. The soil depth that comes out of the EFAS archive is the cumulative depth from the top of the surface to the bottom of each layer.

What do you mean by wetness of leaves?

Leaf wetness. Leaf wetness is a meteorological parameter that describes the amount of dew and precipitation left on surfaces. It is used for monitoring leaf moisture for agricultural purposes, such as fungus and disease control, for control of irrigation systems, and for detection of fog and dew conditions, and early detection of rainfall.